1. Field of the Invention
The present invention generally relates to a network application, in particular, to a method and a system for network synchronization enabling all nodes in the network work and sleep at the same time.
2. Description of Related Art
Along with the progress of the wireless network technology, in many existing network architectures, information is transmitted in a wireless transmission manner. In a wireless sensor network (WSN), a sensor node obtains a sensing data, and a router node sends the data back to a coordinator node in the wireless transmission manner, such that a computer system connected to the coordinator node may obtain and apply the integrated data. The WSN becomes more and more popular because of the advantages such as convenient deploying and low maintaining cost. In addition, most of the sensor nodes have a sleeping capability to reduce the power consumption, such that the longer lifetime is one of the reasons why people increasingly attach importance to the WSN.
However, in the WSN architecture, only the sensor node may simply achieve the purpose of saving the power by sleeping. The reason is that the router node transmits data packets, so usually a permanent power source must be set to maintain the transmission smoothness of the wireless network. However, when the WSN is applied to an outdoor environment, the obtaining and the wiring of the permanent power source are not quite easy. Usually, soon after the wiring of the power source is finished, the line must be disassembled as the project is end. Therefore, it increasingly becomes a trend of using a battery to supply power for the whole WSN. However, under the situation of supplying power by using the battery instead of the permanent power source, it is a quite important topic how to ensure the transmission smoothness of the data and save the power consumption of the battery by using a sleeping mechanism.
Recently, for the method of making the nodes in the network work and sleep at the same time to save the power, the radio frequency (RF) hardware is added to serve as the tool of receiving sync-information or waking up the nodes. However, by using the manner, the hardware cost is increased, in addition, a signal coverage and the power consumption of the RF must be taken into consideration. Moreover, in order to make the nodes in the network work or sleep at different time, a complete lower layer support is required. Further, the lower layer of the network, for example, a physical layer or a media access control layer, must have a time-shared scheduling technique being time division multiple access (TDMA), so as to support the sending and the receiving of the data packet on the upper layer. However, usually it takes quite a long time to set the standard of the lower layer, and the software of all network lower layers must be developed matching with the standard, such that whole architecture of the network loses flexibility, and cannot be widely applied to various demands.